Science Says: Jack Frost nipping at your nose ever later
Across the United States, the year's first freeze has been arriving further and further into the calendar. That's according to more than a century of measurements from weather stations nationwide.
Scientists say it is yet another sign of the changing climate. This has good and bad consequences for the nation. There could be more fruits and vegetables. But there also could be more allergies and pests.
"I'm happy about it." That's according to Karen Duncan. She is from Streator, Illinois. Her flowers are in bloom because she's had no frost this year yet. She had none last year at this time either. On the other hand, she said just last week it was too hot and buggy to go out. For her, that means in late October, near Chicago.
The trend of ever later first freezes appears to have started around 1980. That's according to an analysis by The Associated Press of data. It came from 700 weather stations across the U.S. going back to 1895. It was compiled by Ken Kunkel. He's a meteorologist at the National Oceanic and Atmospheric Administration's National Centers for Environmental Information.
Kunkel compared the first freeze from each of the 700 stations to the station's average for the 20th Century. Some parts of the country experience earlier or later freezes every year. But on average freezes are coming later.
The average first freeze over the last 10 years, from 2007 to 2016, is a week later than the average from 1971 to 1980. This is before Kunkel said the trend became noticeable.
This year, about 40 percent of the Lower 48 states have had a freeze as of Oct. 23. That is compared to 65 percent in a normal year, according to Jeff Masters. He is meteorology director of the private service Weather Underground.
Duncan's flowers should be dead by now. The average first freeze for the 20th century was Oct. 15. That's according to data from the weather station near her in Ottawa, Illinois. The normal from 1981 to 2010 based on NOAA computer simulations was Oct. 19. Since 2010, the average first freeze is on Oct. 26. Last year, the first freeze in Ottawa came on Nov. 12.
Last year was "way off the charts" nationwide, Kunkel said. The average first freeze was two weeks later than the 20th century average. And the last frost of spring was nine days earlier than normal.
Overall the United States freeze season of 2016 was more than a month shorter than the freeze season of 1916. It was most extreme in the Pacific Northwest. Oregon's freeze season was 61 days. This is two months shorter than normal.
Global warming has helped push the first frosts later. That's according to Kunkel and other scientists. Also at play, though, are natural short-term changes in air circulation patterns. But they too may be influenced by man-made climate change.
This shrinking freeze season is what climate scientists have long predicted according to Jason Furtado. He's a University of Oklahoma meteorology professor.
A shorter freeze season means a longer growing season and less money spent on heat. But it also hurts some plants that require a certain amount of chill, such as Georgia peaches, said Theresa Crimmins. She is a University of Arizona ecologist. Crimmins is assistant director of the National Phenology Network . Phenology is the study of the seasons and how plants and animals adapt to timing changes.
Pests that attack trees and spread disease aren't being killed off as early as they normally would be, Crimmins said.
In New England, many trees aren't changing colors as vibrantly as they normally do or used to because some take cues for when to turn from temperature, said Boston University biology professor Richard Primack.
Clusters of late-emerging monarch butterflies are being found far further north than normal for this time of year, and are unlikely to survive their migration to Mexico.
Kevin Trenberth is a climate scientist at the National Center for Atmospheric Research. He said natural variability, especially an El Nino, made last year exceptional for an early freeze, but "it represents the kind of conditions that will be more routine in a decade or two" because of man-made climate change.
"The long-term consequences are really negative," said Primack. That’s because shorter winters and hotter temperatures are also expected to lead to rising seas that cause worse flooding during heavy storms.
In suburban Boston, Primack and his wife are still eating lettuce. They are still eating tomatoes and green beans. They are from their garden. And they are getting fresh figs off their backyard tree almost daily.
"These fig trees should be asleep," Primack said.